In the field of ultrasound transducer for three-dimensional imaging transducer probes are designed by integrating a two-dimensional array of acoustic transducer elements. The transducer elements are typically formed of piezoelectric materials for emitting pressure waves. The transducer elements are usually also used to detect ultrasound reflections for three-dimensional imaging. The transducer elements are typically controlled or driven by ASICs having integrated driver elements for driving the transducer elements separately.
The existing 3D ultrasound transducers are used for transcutaneous and transesophageal imaging and provide an imaging frequency in the range of 2 to 10 MHz. In this imaging frequency range, the ASICs for driving the transducer elements are designed to have a circuitry to control, transmit and receive the acoustic signal in an array that corresponds to the array of a single transducer element. The size of the transducer elements is determined by the imaging requirements of the certain application, i.e. the frequency and the field of view of the ultrasound transducer. Typically a pitch of the transducer elements in a two-dimensional array is between 100 and 300 μm.
For catheter-based imaging devices and systems the currently available imaging transducer probes and driver devices are too large and operate at two low frequencies for providing a necessary two-dimensional and three-dimensional imaging inside the organs, e.g. inside the heart. In particular for applications to examine the heart, the transducer probes have to provide guidance and location information for ablation procedures and structural heart repairs. Those applications need higher frequencies, e.g. 15-60 MHz in order to provide the required imaging characteristics. Further, to achieve the frequency and size requirements of the catheter-based application, Capacitive Micromachined Ultrasound Transducers (CMUTs) can be employed replacing the piezoelectric transducer elements. The CMUTs can provide reasonable acoustic performance at higher frequencies and smaller dimensions than the piezoelectric material and can be manufactured using cheap semiconductor processing techniques.
A possibility to reduce the dimensions of the driver device is known from US 2006/0264747 A1. The microbeam former channels of this driver device are combined to clusters having a common voltage source or common current source. However, due to the large amount of high voltage transistors being integrated in the ASICs the size of the driver device is still too large to be accommodated in a catheter-based transducer probe.